Polysilazane compounds can be generally converted into siliceous substances by heating, and the obtained siliceous substances have such excellent insulation properties that they are practically used as materials of insulating films in the electrical and electronic fields. However, if the polysilazane compounds are simply used, the conversion into the siliceous substances proceeds very slowly and needs high temperature. Since there is thus large room for improvement, various studies have been carried out to overcome the problems.
In order to improve the above problems, it is proposed to reform the polysilazane compounds themselves or to incorporate particular additives into polysilazane-containing compositions. For example, an N-heterocyclic compound (described in, for example, Patent document 1), an alkanol amine (described in, for example, Patent document 2) or an amine and/or acid (described in, for example, Patent document 3) is added as the additive into a polysilazane-containing composition so that the composition can form a siliceous film at a low temperature. The amine compounds described as the additives in the above documents are also used in a composition containing a diamine compound for other purposes such as reducing film-roughness or avoiding coating-ununiformity (described in, for example, Patent documents 4 and 5), and further they are still also used in a composition containing a polyamine compound for the purpose of hardening epoxy resin (described in, for example, Patent document 6).
A dense siliceous film can be obtained if the polysilazane-containing composition incorporating an N-heterocyclic compound additive, which is described in Patent document 1, is allowed to stand for 1 week under environmental conditions, preferably, is fired at 150° C. or more. However, it is desired to provide a polysilazane-containing composition which can favorably form a dense siliceous film more rapidly under environmental conditions or by firing at a lower temperature. Meanwhile, the N-heterocyclic compound is liable to have low solubility to a solvent. Accordingly, when added into the composition, the N-heterocyclic compound is generally dissolved in an organic solvent having high dissolution capacity, namely, in an aromatic hydrocarbon. However, since the aromatic hydrocarbon is generally very volatile and highly harmful to the human body, it is strongly required nowadays to reduce the amount in the solvent. In consideration of that, it is much desired to provide a polysilazane-containing composition which can form a siliceous film more rapidly and at a lower temperature and, at the same time, which contains a small amount of aromatic hydrocarbon solvent.
In contrast, various solvents are usable in the polysilazane-containing composition incorporating an amine and/or acid additive, which is described in Patent document 3. However, in order to form a dense siliceous film, it is necessary to bring the composition into contact with steam at a high temperature for a long time. This means that, in view of forming a dense siliceous film by low temperature firing under environmental conditions, there is still room for improvement.
Various solvents are also usable in the polysilazane-containing composition incorporating an alkanol amine, which is described in Patent document 2. Further, this composition can form a dense siliceous film by low temperature firing. For forming a dense siliceous film, the alkanol amine additive is made to react with the polysilazane compound, and thereby the polysilazane compound is reformed into a useful substance. However, since this reaction proceeds with violent heat generation and foaming, the alkanol amine must be diluted in a solvent and then added gradually for a long time. Accordingly, from the viewpoints of efficiency and cost in mass-production, there is room for improvement.
Patent documents 4 and 5 disclose a general formula representing a relatively wide scope of amine compounds. In the documents, it is described that coating ununiformity can be reduced by incorporating those amine compounds into a polysilazane-containing composition. On the other hand, however, the documents are silent about formation of a siliceous film obtained from the polysilazane-containing composition by low temperature firing. Further, the present inventors' study has revealed that any of the polysilazane-containing compositions disclosed in the documents, such as compositions incorporating hexamethylenediamine, p-phenylenediamine, and N,N,N′,N′-tetramethylethylenediamine, cannot form a fully satisfying siliceous film by low temperature firing. Accordingly, it is found that there is still room for improvement.
[Patent document 1] Japanese Patent Laid-Open No. H11 (1999)-116815
[Patent document 2] Japanese Patent Laid-Open No. H11 (1999)-60736
[Patent document 3] Japanese Patent Laid-Open No. H9 (1997)-31333
[Patent document 4] Japanese Patent Laid-Open No. H8 (1996)-176511
[Patent document 5] Japanese Patent Laid-Open No. H8 (1996)-176512
[Patent document 6] Japanese Patent Laid-Open No. 2004-536196
[Patent document 7] Japanese Patent Publication No. S63 (1988)-16325
[Patent document 8] Japanese Patent Laid-Open No. S61 (1986)-89230
[Patent document 9] Japanese Patent Laid-Open No. S49 (1974)-69717
[Patent document 10] Japanese Patent Laid-Open No. H1 (1989)-138108
[Patent document 11] Japanese Patent Laid-Open No. H1 (1989)-138107
[Patent document 12] Japanese Patent Laid-Open No. H1 (1989)-203429
[Patent document 13] Japanese Patent Laid-Open No. H1 (1989)-203430
[Patent document 14] Japanese Patent Laid-Open No. H4 (1992)-63833
[Patent document 15] Japanese Patent Laid-Open No. H3 (1991)-320167
[Patent document 16] Japanese Patent Laid-Open No. H2 (1990)-175726
[Patent document 17] Japanese Patent Laid-Open No. H5 (1993)-86200
[Patent document 18] Japanese Patent Laid-Open No. H5 (1993)-331293
[Patent document 19] Japanese Patent Laid-Open No. H3 (1991)-31326
[Non-patent document 1] D. Seyferth et. al., Communication of Am. Cer. Soc., C-13, January 1983
[Non-patent document 2] D. Seyferth et. al., Polym. Prepr. Am. Chem. Soc., Div. Polym. Chem., 25, 10 (1984)
[Non-patent document 3] D. Seyferth et. al., Communication of Am. Cer. Soc., C-132, July 1984